You are wandering around in the desert and are exhausted. You meet a nomad
and ask him for the way out. There are only two choices to pick: either go
to the left or to the right. One way leads to an oasis and the other way is "the road
to death". However, the nomad is a liar and you cannot trust him. But you
know for certain that he is systematically lying: If he lies on one day, he
will not lie the following day and vice versa. You can ask him only one question
and he will answer with "yes" or "no".
What question do you ask him in order to survive?
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